package com.hmdp.service.impl;

import cn.hutool.core.lang.TypeReference;
import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import io.lettuce.core.RedisClient;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
@RequiredArgsConstructor
@Slf4j
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    private final StringRedisTemplate stringRedisTemplate;

    private final CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
        //Shop shop = queryWithPassThrough(id);
        //Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);
        //逻辑过期解决缓存击穿
        Shop shop = cacheClient
                .queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //Shop shop = queryWithLogicalExpire(id);
        if (shop == null) {
            return Result.fail("店铺不存在！");
        }
        return Result.ok(shop);
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    /**
     * 逻辑过期解决缓存击穿
     * @param id
     * @return
     */
    public Shop queryWithLogicalExpire(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1、查询Redis缓存商户
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2、判断商户缓存是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3、不存在，直接返回null
            return null;
        }
        //4、存在，缓存命中，需要把json反序列化为对象判断是否过期
        RedisData<Shop> redisData = JSONUtil.toBean(shopJson, new TypeReference<RedisData<Shop>>() {}, false);
        LocalDateTime now = LocalDateTime.now();
        Shop shop = redisData.getData();
        LocalDateTime expireTime = redisData.getExpireTime();
        if(now.isBefore(expireTime)) {
            //5.1未过期，直接返回店铺信息
            return shop;
        }
        //5.2已过期，需要缓存重建
        String lockKey = LOCK_SHOP_KEY + id;
        //6.缓存重建
        // 6.1获取互斥锁
        boolean isLock = tryLock(lockKey);
        // 6.2判断是否获取锁成功
        if (isLock) {
            // 6.3成功，开启独立线程重建缓存
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //缓存重建
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        // 6.4失败，直接返回已过期的商铺信息
        //7、返回
        return shop;
    }

    /**
     * 使用互斥锁解决缓存击穿问题
     * @param id
     * @return
     */
    public Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1、查询Redis缓存商户
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2、判断商户缓存是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3、存在，直接返回商铺信息
            log.info("成功从缓存中读取到用户信息");
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
            //return Result.ok(shop);
        }
        //判断是否为空值
        if(shopJson != null) {
            return null;
            //return Result.fail("店铺信息不存在！");
        }

        //4、实现缓存重建
        //4.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2判断是否获取成功
            if(!isLock) {
                //4.3失败，则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }

            //4.4成功，根据id查询数据库
            shop = getById(id);
            // 模拟重建的延迟
            //Thread.sleep(200);
            //5、不存在，根据id查询商铺信息
            if (shop == null) {
                //将空值存入redis
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                //6、商铺信息不存在，返回错误
                //return Result.fail("查询的商户不存在");
                return null;
            }

            //7、商铺信息存在，将商铺信息写入缓存，返回商铺信息
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }finally {
            //8、释放互斥锁
            unlock(lockKey);
        }

        //9、返回
        //return Result.ok(shop);
        return shop;
    }

    /**
     * 逻辑过期解决缓存击穿
     * @param id
     * @param expireTime
     */
    public void saveShop2Redis(Long id, Long expireTime) throws InterruptedException {
        //1、查询店铺数据
        Shop shop = getById(id);
        Thread.sleep(200);
        RedisData redisData = new RedisData();
        //2、封装逻辑过期时间'
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireTime));
        //3、存入Redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    /**
     * 缓存空值解决缓存穿透问题
     * @param id
     * @return
     */
    public Shop queryWithPassThrough(Long id) {
        log.info("查询商铺信息，id：{}",id);
        String key = CACHE_SHOP_KEY + id;
        //1、查询Redis缓存商户
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2、判断商户缓存是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3、存在，直接返回商铺信息
            log.info("成功从缓存中读取到用户信息");
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
            //return Result.ok(shop);
        }

        //判断是否为空值
        if(shopJson != null) {
            return null;
            //return Result.fail("店铺信息不存在！");
        }
        //4、不存在，根据id查询商铺信息
        Shop shop = getById(id);

        if (shop == null) {
            //将空值存入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            //5、商铺信息不存在，返回错误
            //return Result.fail("查询的商户不存在");
            return null;
        }

        //6、商铺信息存在，将商铺信息写入缓存，返回商铺信息
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //7、返回
        //return Result.ok(shop);
        return shop;
    }

    /**
     * 使用redis设置锁
     * @param key
     * @return
     */
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.MINUTES);
        return BooleanUtil.isTrue(flag);
    }

    /**
     * 释放redis的锁
     * @param key
     */
    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

    /**
     * 更新商铺数据
     * @param shop
     * @return
     */
    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop .getId();
        if (id == null) {
            return Result.fail("id不能为空");
        }
        //1、更新数据库
        updateById(shop);
        //2、删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();
    }
}
